Justness

The quality of being just; conformity to truth, propriety, accuracy, exactness, and the like; justice; reasonableness; fairness; equity; as, justness of proportions; the justness of a description or representation; the justness of a cause.

In value the satisfaction I had in seeing it represented with all the justness and gracefulness of action.
Dryden.

⇒ Justness is properly applied to things, and justice to persons; but the distinction is not always observed.